I was pondering about this, sometimes people ask me to erase data on their drive. So I use a shredding program, which takes a long time. However what if instead of shredding all the files, I'd just use truecrypt to encrypt them. The disk would be useless then no? Would the data still be recoverable for someone without the password? It would be faster no?
I'd use a strong password. I just want to make the data unusable.